According to the Fort Bend County health department, all five people live in the county and were confirmed to have the variant on Wednesday, June 23.
Officials said three of the residents have received only one dose of the COVID vaccine and one had not been vaccinated at all prior to the start of symptoms.
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The vaccination status of the fifth person hasn't been determined yet, but officials said although they all experienced symptoms, no one had to be hospitalized.
"These cases underscore the importance of being fully vaccinated against COVID-19, especially with the delta variant becoming more prevalent in the U.S.," said Dr. Jacquelyn Minter, the director of the county's health and human services department. "Current research shows that two doses of the mRNA vaccines are over 80% effective against the Delta variant."
The delta variant got its name from the World Health Organization, which names notable variants after letters of the Greek alphabet.
Experts say it spreads more easily because of mutations that make it better at latching onto cells in our bodies. In the United Kingdom, the variant is now responsible for 90% of all new infections. In the U.S., it represents 20% of infections, and health officials say it could become the country's dominant type as well.
Studies have shown that the available vaccines work against variants, including the delta variant.
"The best protection that we have against this disease is to be fully vaccinated," said Minter. "If you are not fully vaccinated, we encourage you to wear your mask and to maintain a physical distance from others while in public."
Free vaccines are still available in Fort Bend County.
Researchers in England studied how effective the two-dose AstraZeneca and Pfizer-BioNTech vaccines were against it, compared with the alpha variant that was first detected in the U.K.
The vaccines were protective for those who got both doses, but were less so among those who got one dose.
It's why experts say it's important to be fully vaccinated. And it's why they say making vaccines accessible globally is so critical.